When I sum this rules, I get min 2 Leader cards because deck must be balanced. That means min two 5 star cards (all Leader cards are 5 star), and there is a rule that deck cannot contain more then one 5 star card.

It's called 'One shot' because Timber + Mechakolos or a bunch of FPC cards will be able to kill you in one shot, without fury. Only 11 life see. It'll just be one guess on the first round. If you guess right, you win. If you're wrong, you lose.